//构造函数，类的一部分
var Book = function (isbn,title,autor) { //函数表达式
    this.isbn = isbn;
    this.title = title;
    this.autor = autor;
}
Book.prototype = {
    checkIsbn: function () {},
    borrow: function () {console.log('book的');}
}
var xhs = new Book('001','小黄书','大黄');
Book.prototype = {
    checkIsbn: function () {},
    borrow: function () {console.log('aaa');}
}
xhs.borrow()
var sjms = {borrow : function(){console.log('自己的');}};
//空对象
Book.call(sjms,'002','葵花宝典','金庸')
sjms.__proto__ = Book.prototype
// sjms.borrow()
console.log(sjms.__proto__);
sjms.borrow()
console.log(sjms.toString());